This application claims the benefit of Japanese Application, Nos. 9-048458 and 9-169669 which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a display device and more specifically to a display device which is installed on or near a specular surface of an optical finder of a silver salt camera or the like, superimposes a pattern on a finder image and displays the pattern. The present invention also relates to a camera having this display device.
2. Description of the Prior Art
A display device for performing a predetermined display in a finder of a camera or the like has heretofore adopted a method in which a liquid crystal panel filled with a twist type liquid crystal material is controlled by a transparent electrode (ITO). The method using a polymer dispersed liquid crystal has also adopted the method in which this liquid crystal is filled over a glass material surface, a control is operated by the transparent electrode and the display is performed. Recently, the method in which information is displayed in the finder of the camera by the use of a host/guest type liquid crystal has been also adopted.
In case of the camera, many fine prisms are aligned on a finder surface so that they may be shaped into characters and symbols to be displayed. A light is emitted from an upper or a lower portion of the finder, whereby a reflected light directly comes into eyes through the finder so that the characters and symbols are displayed.
Any of the above-described methods has both merits and demerits. Any methods are not said to be desirable. The display device using the twist type liquid crystal has a visual field angle. The display is limited depending on a direction of observation. Furthermore, since a rotating angle of the liquid crystal is controlled, conditions are disadvantageously varied due to a temperature or the like. Thus, a contrast control is required. This results in inconvenience. In case of another arrangement, that is, when the twist type liquid crystal is used for the finder of the camera so that a transmission-type superimposition is performed, a polarizing plate is required for a liquid crystal display. Thus, since a light transmittance is 50% at maximum in a portion which transmits the light, a visual field of the finder is considerably darkened. Therefore, a subject image to be picked up in the finder cannot be clearly seen.
Furthermore, in the method using the polymer dispersed liquid crystal as it is, when the polymer dispersed liquid crystal is turned off, it is cloudy opaque or white turbid and the light is thus scattered. When the polymer dispersed liquid crystal is turned on, it is transparent. Due to such properties, a logic circuit for turning off a portion to be displayed must be constructed. This causes a problem. The fact that a display portion is displayed in a turn-off state does not mean that a display logic has only to be reversely operated. Thus, the problem is not solved.
In case of the commercially available/typical liquid crystal controlled by front and rear electrodes, only when both the front and rear electrodes are turned on, the display portion is visibly recognized. Both the electrodes are therefore arranged so that routes of the front and rear electrodes guided to the display portion may not overlap with each other. Both the electrodes are turned on, whereby it is possible to visibly recognize the display portion alone where the electrodes overlap with each other. This means that the portion alone, where a logical product of the front and rear electrodes is obtained, is displayed in accordance with the logic indicating that the display is accomplished by a turn-on.
However, if this display logic is reversely operated, when at least one of the front and rear electrodes is turned off, the display is performed. Thus, a desired portion alone cannot be displayed by controlling the two electrodes. In this case, the display portion is displayed by a logical sum of both the electrodes. In this method, the selective and limited display cannot be therefore performed. Since the routes of the electrodes are displayed, it is difficult to obtain the high-quality display device.
The method reflecting the light by a microprism is different from the method in which the display portion is blackly emerged by shutting out the light from the portion to be displayed. That is, since the display portion apparently emits the light, the display portion has excellent visibility. Advantageously, the display can be clearly seen even if a background is dark. However, even when the display portion is not displayed, the display portion does not transmit the light and the light remains shut out from the display portion. Thus, this portion disadvantageously conceals the background. Also required is a three-dimensional arrangement in which a projecting portion is located over or under a display surface. Therefore, disadvantageously, an installation is considerably limited for loading this arrangement. It is thus necessary to manufacture a change in the display contents to correct or reform an expensive plastic injection mold. This causes not only a cost problem but also a problem of waste of time. This is a factor which prevents the display contents from being optionally changed as required.
Furthermore, heretofore, in the camera having an AF (auto-focus control) mechanism, an AF auxiliary light irradiating device for irradiating the subject with an AF auxiliary light has been exclusively disposed on a camera body. At the time of the dark background or the like, the subject is irradiated with a luminous flux from a light source such as an LED of this device. The reflected light is detected, whereby an auto-focus control is performed. This device is individually disposed in the camera in order to use the AF auxiliary light.
A single-lens reflex camera is provided with a mechanism in which a diaphragm value shown on a lens ring of a lens attached to the camera is projected into the finder visual field in order that the diaphragm value is confirmed in the finder at the time of a pick-up. This mechanism includes a lens ring illuminating device having an illumination optical system for partially illuminating the lens ring in order to effectively perform such a projection even in a dark environment. This illumination optical system directly illuminates a mark indicative of the diaphragm value of a diaphragm member, whereby the mark of the diaphragm value can be readably projected into the finder even when a natural light is weak.
However, if an additional optical system or the like is arranged in the camera in order to project the AF auxiliary light as described above, this is a considerable burden on the camera having a limited space. Furthermore, since an additional member is needed, a cost is increased. Thus, this device is not desirable in view of the cost. This problem is similarly caused in case of the device for illuminating the diaphragm member.
It is an object of the present invention to provide a display device having excellent visibility and no dependence on a visual field angle and capable of accomplishing a high-quality display and of immediately switching both of a display brightly emerged in a background and a dark display in accordance with a subject condition and a user""s request.
In order to solve the above problem, a display device of the present invention comprises: a pair of plate-like light transmittable members; a display member located so as to form a predetermined pattern between a pair of light transmittable members, the display member being composed of a material whose light transmittance is electrically changed; and a pair of light transmittable electrodes, at least one of a pair of light transmittable electrodes having a shape corresponding to the pattern, a pair of light transmittable electrodes being formed on a pair of light transmittable members and for electrically controlling the material.
According to this display device, the material located in the pattern between the light transmittable members has the same shape as a predetermined pattern. The light transmittance of the material is electrically changed. Thus, when the light transmittance of the material is controlled by the electrodes so that it may be lower, a predetermined pattern transmits less light than the light transmittable members. Therefore, the pattern is displayed in a predetermined shape. When the light transmittance is controlled so that it may be higher, the pattern can transmit the light substantially as much as the light transmittable members. Therefore, the pattern is not displayed. Furthermore, in the display device of the present invention, the display member comprises a plurality of display patterns arranged independently of each other. According to this arrangement, since a plurality of patterns can be independently controlled, they can be independently displayed.
Furthermore, in the display device of the present invention, the display member further comprises a pattern forming member, a concavity is formed on the pattern forming member so that it may be shaped correspondingly to the pattern, and the concavity is filled with the material. According to this arrangement, the concavity having a predetermined pattern is formed in the pattern forming member and the concavity is filled with the material, whereby the pattern having a predetermined shape can be easily arranged.
Furthermore, in the display device of the present invention, the material is a polymer dispersed liquid crystal. The polymer dispersed liquid crystal is composed of a polymer/liquid crystal composite material using a nematic liquid crystal. The polymer dispersed liquid crystal is a field effect type and a light scattering type. The polymer dispersed liquid crystal does not require a polarizing plate. When an electric field is not applied to the polymer dispersed liquid crystal, the polymer dispersed liquid crystal is cloudy opaque or white turbid. The polymer dispersed liquid crystal allows an external light to be scattered. The polymer dispersed liquid crystal does not transmit the external light. When the electric field is applied to the polymer dispersed liquid crystal, the light transmittance is increased and becomes extremely high. The polymer dispersed liquid crystal is characterized by an electric field dependent scattering body exhibiting the higher light transmittance.
Therefore, when the electric field is applied to the scattering body and the scattering body is changed to a light transmittable body, a refractive index of the light transmittable body is substantially the same as that of a pair of light transmittable members. Thus, when the electrodes are turned on, these two materials have substantially the same optical properties. An observer cannot distinguish these materials from each other. Actually, the polymer dispersed liquid crystal is a transparent plate. The pattern is not thus displayed.
When the scattering body is in the scattering state, that is, when the electrodes are turned off, the light is scattered in the portion where the scattering body exists. The polymer dispersed liquid crystal is cloudy opaque or white turbid in the portion where the pattern is formed. A background light which is the external light must be scattered and pass through the scattering body. Thus, a luminous energy is attenuated and the light is shut out. Assuming that the system is illuminated by the background light alone, the scattering body is blackly emerged in the background light, whereby the display pattern is displayed. This pattern display is referred to as a xe2x80x9clight shutout displayxe2x80x9d.
The display device of the present invention further comprises illuminating means, wherein, when the light transmittance of the material is controlled so that it may be lower, the illuminating means illuminates the material whereby the pattern is brightly displayed by a scattered light.
When the device is arranged so that the illuminating means may illuminate the pattern, the light is scattered by the pattern-shaped material whose light transmittance is controlled so that it may be lower. Thus, an illuminating light is scattered in the portion where the material exists. This scattered light allows the pattern-like material to be brightly seen. When the observer looks at the pattern, the pattern looks as if the pattern itself glowed. This pattern display is referred to as an xe2x80x9cself-light-emitting displayxe2x80x9d.
In case of such a self-light-emitting display, the illuminating means can be arranged so that the light thereof may be incident on end surfaces of a pair of light transmittable members. Furthermore, the illuminating means can be arranged so that the light thereof may pass through the surfaces of a pair of light transmittable members and the pattern may be illuminated with the light.
The display device of the present invention further comprises: illumination-switching determining means for determining whether the illuminating means is switched on or off; and display selecting means for selecting whether or not the pattern is displayed.
According to this arrangement, the illuminating means can be controlled by the illumination-switching determining means. By switching whether the illuminating means is turned on or off, it is possible to switch the self-light-emitting display and the light shutout display. A display type can be determined in accordance with a luminance of the background or the user""s request. Moreover, the electrodes are controlled by the display selecting means and the light transmittance of the material is thus changed, whereby whether or not the pattern is displayed can be switched.
Furthermore, the display device of the present invention is applied to a camera. In the camera, the display device is installed on or near an image plane of an optical finder, superimposes the pattern on a finder image and displays the pattern. In this case, the camera may be any one of a video camera, a digital still camera, a silver halide camera or the like.
According to the present invention, in the camera in which the display device having the illuminating means is installed on or near the image plane of the optical finder, superimposes the pattern on the finder image and displays the pattern, the camera comprises: photometering means for measuring the luminance of a subject, wherein the illumination-switching determining means is automatically controlled in accordance with subject luminance information from the photometering means.
According to this arrangement, whether the illuminating means is switched on or off can be controlled in accordance with the subject luminance information from the photometering means disposed for a camera automatic exposure or the like. Thus, when the subject is dark and the background is dark, the illuminating means is switched on whereby the pattern can be brightly displayed. When the background is bright, the illuminating means is switched off whereby the pattern can be darkly displayed. Therefore, the pattern can be darkly or brightly displayed in accordance with a brightness/darkness of the background. The pattern can be easily seen and displayed at all times.
According to the present invention, a method of manufacturing the display device comprises the steps of: forming light transmittable electrodes on a pair of plate-like light transmittable members; forming at least one of the electrodes so that the one electrode may have a predetermined shape corresponding to the display pattern; coating a photo-setting agent on the surface of one of the light transmittable members; irradiating the photo-setting agent layer with the light through a photomask having a light shutout pattern having a predetermined shape corresponding to the display pattern; removing the portion corresponding to the pattern of the photomask from the photo-setting agent layer and forming a concavity having the shape corresponding to the display pattern; filling the concavity with the material whose light transmittance is electrically changed; and fixing the other light transmittable member on the photo-setting agent layer.
According to this arrangement, it is possible to efficiently precisely form the concavity which has the shape corresponding to the display pattern and is filled with the material. The high-precision display device can be efficiently manufactured.
According to the present invention, in the method of manufacturing the display device, the material is the polymer dispersed liquid crystal, the step of fixing the other light transmittable member on the photo-setting agent layer includes the steps of: coating an ultraviolet-curing adhesive on the photo-setting agent layer; locating the other light transmittable member on the photo-setting agent layer; and irradiating the ultraviolet-curing-adhesive-coated portion and the polymer dispersed liquid crystal with an ultraviolet light.
According to this arrangement, when the other light transmittable member is fixed on the photo-setting agent layer by the use of the ultraviolet-curing adhesive, the ultraviolet-curing adhesive portion is irradiated with the ultraviolet light. At the same time, the polymer dispersed liquid crystal is also irradiated with the ultraviolet light, whereby it is possible to obtain desired physical properties of the polymer dispersed liquid crystal.
It is another object of the present invention to provide a camera capable of comprising functions such as an AF auxiliary light irradiating mechanism and a diaphragm member illuminating mechanism without requiring an additional space and a finder display device for realizing this camera.
In order to achieve a second object, according to the present invention, the light from a light source for displaying a region to be auto-focused or the like in the finder can be used as an AF auxiliary light, the light for illuminating a diaphragm member or the like. That is, according to the present invention, the finder display device comprises: a display member having a display portion for performing a predetermined display in a finder; illuminating means for illuminating the display portion of the display member; and an optical system for guiding the light outgoing through the display member to an external member to be illuminated.
According to the present invention, the light for illuminating the display portion is allowed to outgo from the display member. This outgoing light is guided to the external member to be illuminated. Thus, the light for illuminating the display portion is guided outward, whereby this illuminating light can be used as, for example, the AF auxiliary light and the light for illuminating a lens barrel. Moreover, since the particular light source is not required for the AF auxiliary light irradiating mechanism and a lens barrel illuminating mechanism, the mechanisms can be easily arranged whereby a cost is reduced.
The optical system can comprise optical gate means for selectively guiding the light outgoing through the display member to the member to be illuminated. Thus, for example, only when the AF auxiliary light and the lens tube illuminating light are required, the lights can be guided to the members to be illuminated. If unnecessary, the light can be reduced and shut out.
The display member comprises a plate member for forming an optical waveguide, and the illuminating means and the optical system can be disposed near one end surface and the other end surface of the plate member, respectively. Thus, the display member comprises the plate member, the light is incident on one end surface of the plate member, and the plate member is used as the optical waveguide, whereby the display portion can be illuminated. Moreover, the light is allowed to outgo from the other end surface of the plate member, whereby the illuminating light can be guided outward.
The camera can comprise the above-described finder display device. Thus, when the camera comprises the AF auxiliary light irradiating mechanism, the lens barrel illuminating mechanism or the like, it is not necessary to provide an additional light source. These mechanisms can be easily arranged. This can contribute to a cost reduction of the camera.
The subject is illuminated by the light outgoing from the optical system. Thus, even if the subject is dark and a focus detection is thus difficult, the subject is illuminated whereby the focus detection can be performed.
The camera further comprises a mark member. The subject can be illuminated through the mark member by the light outgoing from the optical system. Thus, the subject can be illuminated so that it may have a bright/dark pattern, whereby the focus can be detected from the subject having little pattern itself.
The mark member is a logo mark shown on the surface of the camera. Thus, the logo can be projected on the subject, whereby it is possible to expect an advertisement effect for establishing an identity by a logo. The display portion of the display member displays the region in which the focus detection is performed. This makes the region for the focus detection clear.
The camera further comprises a lens diaphragm member. The lens diaphragm member is illuminated by the light outgoing from the optical system whereby diaphragm information shown on the lens diaphragm member can be visually read by the light reflected from the lens diaphragm member. Thus, the diaphragm member illuminating mechanism can be arranged by the use of the light for illuminating the display portion of the finder display device. Therefore, even when a natural light is weak, the diaphragm information on the lens diaphragm member can be visually recognized.
The device of the present invention may comprise the display member to be the optical waveguide; the light source such as an LED for illuminating the display member; an incident portion disposed on one end of the display member; an outgoing portion disposed on the opposite end; a light shutter member for shutting out a luminous flux and reducing the light or for light transmitting the light; and the optical system for spreading the luminous flux at an appropriate angle or a reflecting member and the optical system for reflecting the light and for illuminating the diaphragm member of the attached lens tube.